Magnetic anomalies of the southeastern part of the King Through, Northeastern Atlantic

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Abstract

The results of geomagnetic studies of the southeastern part of the King Trough and the central segment of the Azores-Biscay Rise, carried out in the Northeast Atlantic in 2023 on the 55th cruise of the RV “Akademik Nikolai Strakhov” are presented. These are the first systematic measurements of the magnetic field, which made it possible to construct a map of the magnetic anomaly of the study area. Intense magnetic anomalies were identified on the ridges bounding the King Trough, as well as linear anomalies on its flanks and in the southeastern part of the study area in the central segment of the Azores-Biscay rise. Spectral analysis and transformations of the magnetic anomaly indicate the existence of deep anomalies within the polygon. The intense deep anomalies are of volcanic origin and were formed in a different geomagnetic epoch than the deep parts and flanks of the King Trough. The results confirm the hypothesis of a complex two- or multi-stage formation of geological structures at the King Trough, with the exception of its southeastern part, which belongs to the Azores-Biscay Rise.

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About the authors

A. N. Ivanenko

Shirshov Institute of Oceanology RAS

Email: palshin@ocean.ru
Russian Federation, Moscow

A. M. Gorodnitskiy

Shirshov Institute of Oceanology RAS

Email: palshin@ocean.ru
Russian Federation, Moscow

N. A. Palshin

Shirshov Institute of Oceanology RAS

Author for correspondence.
Email: palshin@ocean.ru
Russian Federation, Moscow

I. A. Veklich

Shirshov Institute of Oceanology RAS

Email: palshin@ocean.ru
Russian Federation, Moscow

V. L. Lyubinetskiy

Shirshov Institute of Oceanology RAS

Email: palshin@ocean.ru
Russian Federation, Moscow

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Supplementary files

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2. Fig. 1. Bathymetric map of the eastern flank of the Mid-Atlantic Ridge [21]. Ocean depth – D, m. The main structural elements and the position of the research area during the 55th cruise of the R/V “Akademik Nikolay Strakhov” (Torg King testing ground) are shown.

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3. Fig. 2. Bathymetric map of the King Trough test site (depth D, m) and the route of the R/V Akademik Nikolay Strakhov on its 55th cruise (black lines). Thin black lines show the positions of the archival magnetic field measurements. Main structural elements: CB – central depression, SE – southern depression, EB – eastern depression, ZW – western elevation, TP – Peak trough, TF – Frin trough, 1 – Antialtair Mountain, 2 – Grigory Zima Mountain [26].

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4. Fig. 3. Map of anomalous magnetic field graphs, Ta, nT, superimposed on a bathymetric map (depth in meters) [26].

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5. Fig. 4. Anomalous magnetic field Ta, nT, and linear magnetic anomalies at the King Trough test site. Black circles are data from the catalogue [24], dashed lines are linear anomalies identified based on the cruise data (see also text). Numbers are numbers of magnetic anomalies. Depth isolines are shown to highlight the main structures. The main structural elements are shown in Fig. 2. Roman numerals designate morphostructural provinces: I – flank structures of the MAR; II – southeastern; III – central segment of the Azores-Biscayne Rise; IV – southeastern basins; V – southeastern end of the King Trough; VI – central part of the King Trough [26].

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6. Fig. 5. Estimation of depths from the ocean surface to sources of magnetic anomalies at the testing site by the radially averaged spectrum of anomalies (red line) and by the radially averaged and frequency-normalized spectrum of anomalies (blue line). S is the power spectrum of magnetic anomalies, f is the spatial frequency.

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7. Fig. 6. Magnitude of the anomalous magnetic field M, nT, at sea level (a) and at an altitude of 15 km (b). Shown are isolines of the bottom depth to highlight the main structures. Legend: A, B and C are the highlighted deep anomalies (see text). Roman numerals indicate morphostructural provinces (see Fig. 4), black lines are the boundaries between provinces [26].

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8. Fig. 7. Horizontal gradient of the anomalous magnetic field GT, nT/km, at sea level (a) and at an altitude of 15 km (b). The bottom depth contours are shown to highlight the main structures. Legend: A, B and C are the highlighted deep anomalies. The Roman numerals indicate the morphostructural provinces (see Fig. 4), the black lines are the boundaries between the provinces [26].

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9. Fig. 8. Bouguer gravity anomalies, ∆GB, mGal (a), and residual gravity anomalies ∆Gres, mGal (b). Shown are the bottom depth contours to highlight the main structures. Legend: A, B, and C are the highlighted deep magnetic field anomalies. Roman numerals denote morphostructural provinces (see Fig. 4) [26].

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